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Old Jan 20, 2013, 07:13 PM
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United States, NC, Concord
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Walbro WT645 carb rebuild problem

Hey guys -- scratching my head trying to figure out what is up with this Walbro carb that I have rebuilt. It had been used probably 3 years on my G26 Zenoah with electronic ignition. Then this season it just wouldn't start my G26. seemed like it wasn't putting gas into the cylinder and couldn't see any gas coming through the input line to the carb (no drawal or suction)...put a new carb kit in it figuring that it was just gummed up with old gas....got it back together and go to prop the plane over and it is just flooding out the plane after only 4 to 5 props..gas dripping out of carb etc. removal of spark plug and an ounce of gas comes out....I even replaced the metering valves and jet and the adjustment looks right on.. I'm pretty sure that all diaphrams are positioned correctly. I used carb cleaner with the straw to "jet" out all ports so I think it is all clean. Replaced both screens, welch plugs etc...I just have no other ideas what could be wrong. Got tired of foolin with it and ordered a brand new carb and put it on plane and the plane fires right up....The old carb is not metering properly for some unknown reason. I hate to throw the thing away and really scratching my head on this one...Any ideas???
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Old Jan 20, 2013, 07:57 PM
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USA, TX, Grapevine
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I have had a problem like that. In my case the pivot lever was bent down slightly causing it to not let the fuel inlet valve close off the fuel. The regulator diaphragm had also been a problem on another carb. The diaphragm had sort of stretched out over time and wouldn't put pressure on the pivot arm anymore.
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Old Jan 21, 2013, 07:20 PM
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Muncie, IN
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http://wem.walbro.com/distributors/s...s/WTseries.pdf
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Old Jan 21, 2013, 08:25 PM
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United States, NC, New Bern
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sounds like the regulator needle isn't closing all the way. may have some gunk stuck on the seat.

also on the regulator side the thick gasket goes on first then the regulator diaphragm. if you have it the other way around it may be opening up the regulator to much to early.
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Old Jan 26, 2013, 08:46 PM
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United States, NC, Concord
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Quote:
Originally Posted by miltac View Post
sounds like the regulator needle isn't closing all the way. may have some gunk stuck on the seat.

also on the regulator side the thick gasket goes on first then the regulator diaphragm. if you have it the other way around it may be opening up the regulator to much to early.
yep I am aware of that and do have the diaphram and gasket in proper order but yes you are right about the reverse order and what that would do as far as lever movement being off....thanks for the reply guys...the gunked jet seat could be something that I may need to think about more and do a more thourgh cleaning...maybe check the lever for being bent or out of spec.
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Old Jan 27, 2013, 06:26 AM
Two left thumbs
Muncie, IN
Joined Sep 2006
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It is not rare to have a stuck check valve in the high speed discharge nozzle. Take the time to read the Walbro service manual posted above so you can understand the flow of fuel in your carb. Note the little disc inside the nozzle #19 on the diagram on page 2.
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Old Jan 28, 2013, 10:47 AM
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United States, IA, Rockwell
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Also, on these carbs do not used compressed air to blow then out. And, do not use carb and choke cleaner. It is too aggressive. I do use brake parts cleaner though.

The brake parts cleaner and no compressed air is a recommendation from our Stihl service trainer. I'm thinking he has seen many more issues than all of us put together and should know what he is talking about.

Ken
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Old Jan 28, 2013, 01:44 PM
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Muncie, IN
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Quote:
Originally Posted by kenh3497 View Post

The brake parts cleaner and no compressed air is a recommendation from our Stihl service trainer.
Ken
You talking about Eddie in Virginia Beach?

I've had good luck soaking carbs overnight in Sea Foam. Saved one that way today on an old FS 80. Better yet, an ultrasonic cleaner is the ticket. Sea Foam in an ultrasonic will unstick whatever's stuck if it can be unstuck!
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Old Jan 28, 2013, 08:01 PM
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United States, IA, Rockwell
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Quote:
Originally Posted by GeoffinIN View Post
You talking about Eddie in Virginia Beach?

I've had good luck soaking carbs overnight in Sea Foam. Saved one that way today on an old FS 80. Better yet, an ultrasonic cleaner is the ticket. Sea Foam in an ultrasonic will unstick whatever's stuck if it can be unstuck!
Nope, Rick at Mississippi Valley. Never thought about Seam Foam as a cleaner and you are right about the Ultrasonic cleaner. They are the ticket for any cleaning job!!!

Ken
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